Boris Johnson's deputy mayor today insisted that policing numbers in London would remain stable despite the Conservative mayor's decision to tell Scotland Yard to find £472m of savings over three years.

Kit Malthouse, the deputy mayor on policing who also sits as vice-chair of the Metropolitan Police Authority, said there would be "the same number" of police officers in Scotland Yard overall, despite a rise and subsequent dip across the next three years.

The Metropolitan police force has 32,000 officers working across the Greater London area.

Malthouse told the budget and performance committee of the London assembly earlier today that this number would be made "better" as a result of efficiencies made across the force.

Under Operation Herald, a scheme to recruit more civilians to staff custody suites, 900 workers will take over routine policing duties to enable 550 officers to be released to fill frontline vacancies over the next three years.

Dedicated detention officers will fill out custody records to allow a reduction in the numbers of sergeants working in custody blocks, while nurses will dispense certain medical duties currently carried out at greater expense by doctors.

"We will squeeze every bit of value out of every pound," Malthouse said.

The plans were outlined as Malthouse and Tim Goodwin, the Met's acting deputy commissioner, gave evidence regarding Johnson's plans to slash millions from the policing budget.

The cross-party panel heard that planned savings also included merging back-office services such as human resources, and cutting back on training costs by using more officers for frontline duty previously engaged in jobs taken over by civilians.

Goodwin nevertheless conceded that 9% of savings would have to come from frontline services, though he maintained that these could be achieved without cutting back on policing strength.

Goodwin said Scotland Yard was in negotiations with the Home Office over plans to ensure asset recovery investigators were funded by the "villains" being pursued, for example.

Malthouse told the panel that focusing on headline policing numbers was in itself a "stale debate".

"The headline number of police offices is misleading in terms of the capacity to fight crime," he said. "The example often quoted is that there used to be 400 police officers in forensics, now there are none. Is that a reduction in capacity? No actually it is an improvement in efficiency."

Scotland Yard scores 65% on Home Office indicators for the number of police working on the frontline, higher than similar police forces elsewhere, the assembly heard.

Malthouse vowed to improve that figure significantly despite the savings. "It is never going to be 100%," he said, "but you can aspire to it."